Device Manager API — Hardware Devices in MVH Kernel

The device manager maintains a registry of up to 32 hardware devices. Each entry records a numeric ID, a device type drawn from a fixed enumeration, a human-readable name (up to 27 characters), and an online flag indicating whether the device is currently active. You interact with the registry through the five functions described below.

Constants

Constant	Value	Meaning
`DEVICE_MAX`	`32`	Maximum number of devices that can be registered
`DEVICE_NAME_MAX`	`28`	Size of the `name` buffer in `device_info_t`, including the null terminator

Types

`device_type_t`

An enumeration of all recognised device classes.

typedef enum {
    DEVICE_CPU,         /* Processor                     */
    DEVICE_INTERRUPT,   /* Interrupt controller (e.g. APIC / PIC) */
    DEVICE_TIMER,       /* Interval timer (e.g. PIT, HPET)        */
    DEVICE_INPUT,       /* Input device (keyboard, mouse, …)      */
    DEVICE_DISPLAY,     /* Display / framebuffer                   */
    DEVICE_SERIAL,      /* Serial port (e.g. 8250 UART)           */
    DEVICE_CLOCK,       /* Real-time or monotonic clock            */
    DEVICE_BUS,         /* System bus (PCI, ISA, …)               */
    DEVICE_FILESYSTEM   /* Storage / filesystem layer              */
} device_type_t;

`device_info_t`

A snapshot of a single registered device.

typedef struct {
    uint32_t      id;                   /* Unique device identifier            */
    device_type_t type;                 /* Device class                        */
    uint8_t       online;               /* 1 = online / active, 0 = offline    */
    char          name[DEVICE_NAME_MAX];/* Null-terminated display name        */
} device_info_t;

uint32_t

A kernel-assigned identifier that is unique for the lifetime of the registry. IDs are assigned sequentially starting from 0 and are never reused within a single boot.

device_type_t

The device class. Use device_type_name() to convert this value to a printable string.

uint8_t

1 if the device is online and available; 0 if it has been registered but is not yet active or has failed.

char[28]

A null-terminated UTF-8 display name supplied at registration time. Maximum usable length is 27 characters.

Functions

`device_manager_init`

void device_manager_init(void);

Initialise the device manager. You must call this function exactly once during kernel startup, before calling any other device API function. Calling it a second time resets the registry and discards all previously registered devices.

`device_register`

int device_register(const char *name, device_type_t type, uint8_t online);

const char *

required

A null-terminated display name for the device. The name is copied into the registry; you do not need to keep the pointer alive after the call. Maximum length is 27 characters — longer names are truncated to fit DEVICE_NAME_MAX.

device_type_t

required

The device class. Must be one of the device_type_t enumerators listed above.

uint8_t

required

Pass 1 to mark the device as online immediately, or 0 to register it in an offline state.

int

Returns 0 on success. Returns -1 if the registry is full (i.e. DEVICE_MAX devices are already registered).

`device_count`

uint32_t device_count(void);

Return the number of devices currently registered.

uint32_t

The number of entries in the registry, in the range [0, DEVICE_MAX].

`device_list`

uint32_t device_list(device_info_t *devices, uint32_t capacity);

Copy registered device records into a caller-supplied array.

device_info_t *

required

Pointer to an array of device_info_t that will receive the device records. The array must be large enough to hold at least capacity elements.

uint32_t

required

The maximum number of records to write. Pass DEVICE_MAX to guarantee that every registered device is captured.

uint32_t

The number of records written to devices. This is min(device_count(), capacity).

`device_type_name`

const char *device_type_name(device_type_t type);

Return a human-readable string for a device type enumerator.

device_type_t

required

Any device_type_t value.

const char *

A pointer to a null-terminated string such as "CPU", "INTERRUPT", "TIMER", "INPUT", "DISPLAY", "SERIAL", "CLOCK", "BUS", or "FILESYSTEM". The pointer refers to a static string — do not free or modify it. Returns "UNKNOWN" for unrecognised values.

Shell Command

The built-in devices shell command prints a formatted table of every registered device, including its ID, type, name, and online state:

devices

Example

The following example registers two custom devices, then iterates the registry and prints each entry.

#include <mvh/device.h>
#include <stdio.h>

void enumerate_devices(void) {
    /* Initialise the registry once at boot. */
    device_manager_init();

    /* Register a virtual serial port (online) and a stub bus (offline). */
    if (device_register("com1", DEVICE_SERIAL, 1) != 0) {
        /* Registry is full — handle gracefully. */
        return;
    }
    device_register("pci-stub", DEVICE_BUS, 0);

    /* Allocate a buffer large enough for every possible device. */
    device_info_t list[DEVICE_MAX];
    uint32_t count = device_list(list, DEVICE_MAX);

    for (uint32_t i = 0; i < count; i++) {
        device_info_t *d = &list[i];
        printf("[%2u] %-12s  type=%-12s  online=%u\n",
               d->id,
               d->name,
               device_type_name(d->type),
               d->online);
    }
}

Memory

Filesystem

Hardware

Kernel Services

Device Manager API — Hardware Devices in MVH Kernel

Constants

Types

`device_type_t`

`device_info_t`

Functions

`device_manager_init`

`device_register`

`device_count`

`device_list`

`device_type_name`

Shell Command

Example

​Constants

​Types

​device_type_t

​device_info_t

​Functions

​device_manager_init

​device_register

​device_count

​device_list

​device_type_name

​Shell Command

​Example

Constants

Types

`device_type_t`

`device_info_t`

Functions

`device_manager_init`

`device_register`

`device_count`

`device_list`

`device_type_name`

Shell Command

Example